Under 35 U.S.C. xc2xa7 119, this application claims the benefit of German Application No. 10023158.6, filed May 12, 2000, and entitled xe2x80x9cProcess and Means for the Production of a Radiation Device for Carrying Out an Intensity-Modulated Radiotherapy as well as Radiation Device,xe2x80x9d which is incorporated herein by reference.
This invention relates to systems and methods for planning radiation therapy for a patient.
Radiation therapy involves delivering a high, curative dose of radiation to a tumor, while minimizing the dose delivered to surrounding healthy tissues and adjacent healthy organs. Therapeutic radiation doses typically are supplied by a charged particle accelerator that is configured to generate a high-energy electron beam. The electron beam may be applied directly to one or more therapy sites on a patient, or it may be used to generate a photon (e.g., X-ray) beam, which is applied to the patient. With a multi-leaf collimator, the shape of the radiation beam at the therapy site may be controlled by multiple leaves (or finger projections) that are positioned to block selected portions of the radiation beam. The multiple leaves may be programmed to contain the radiation beam within the boundaries of the therapy site and, thereby, prevent healthy tissues and organs located beyond the boundaries of the therapy site from being exposed to the radiation beam.
A typical radiation therapy plan calls for the delivery of series of radiation treatment fractions to the patient over the course of a several days or weeks. Each treatment fraction consists of a sequence of radiation segments with a prescribed cumulative dose intensity profile. Each segment generally has a different intensity profile and, therefore, requires a different leaf arrangement. The time required to deliver a treatment fraction primarily depends on the prescribed cumulative dose and the number of segments to be delivered to the patient. In order to reduce the discomfort patients experience during the delivery of a treatment fraction, efforts have been made to reduce the time needed to deliver treatment fractions to the patient. For example, U.S. Pat. No. 5,663,999 describes a scheme for optimizing the delivery of an intensity modulated radiation beam by selectively combining segments in a single treatment fraction to reduce the total number of segments in the treatment fraction.
The invention features systems and methods of planning a radiation therapy comprising of a series of radiation treatment fractions each comprising a sequence of radiation segments with a prescribed cumulative dose intensity profile to be delivered to a therapy site on a patient.
In one aspect of the invention, a pair of consecutive radiation treatment fractions is generated, wherein each treatment fraction comprises a different set of radiation segments.
Embodiments may include one or more of the following features.
Common radiation segments of two consecutive prescribed radiation treatment fractions may be combined to reduce the total number of radiation segments applied to the patient. The resulting intensity profiles of the two consecutive radiation treatment fractions may be different.
The intensity profiles of the two consecutive radiation treatment fractions may be generated from an initial common intensity profile. The common cumulative dose intensity profile may be divided into a series of layers each corresponding to a predetermined dosage level. The layers preferably are re-assigned to a respective one of the two consecutive radiation treatment fractions. The layers may be re-assigned to the consecutive radiation treatment fractions so that the intensity profiles of the two consecutive radiation treatment fractions are approximately the same. Adjacent layers of the series of layers may be assigned to a different one of the two consecutive radiation treatment fractions. The remaining radiation treatment fractions may be grouped into fraction pairs, wherein the fractions of each pair each has a respective intensity profile generated from layers of a common intensity profile. The treatment fractions of each pair may have different intensity profiles.
The two consecutive radiation treatment fractions may be normalized. For example, the two consecutive radiation treatment fractions may be normalized by increasing the predetermined dosage level of each layer by the same amount to achieve a cumulative radiation dose for each treatment fraction that is substantially the same as the cumulative radiation dose of the common intensity profile. In one embodiment, the radiation treatment fractions may be normalized by substantially doubling the predetermined dosage level of each layer.
In one embodiment, the total number of radiation segments applied to the patient may be reduced further. In this embodiment, the intensity profile of a selected one of the two consecutive radiation treatment fractions may be divided into a plurality of radiation segments. Divided out radiation segments preferably are combined to reduce the total number of radiation segments in the selected treatment fraction.
The invention also features a system, a computer program, and a computer-readable medium carrying instructions for planning the application of a series of radiation treatment fractions, each fraction comprising a sequence of radiation segments with a prescribed cumulative dose intensity profile to be delivered to a therapy site on a patient. The system, computer program, and computer-readable medium each are operable to combine common radiation segments of two radiation treatment fractions to reduce the total number of radiation segments applied to the patient.
Among the advantages of the invention are the following.
The invention combines common radiation segments across the series of the radiation treatment fractions in the overall treatment plan to reduce the total number of segments in each treatment fraction. In accordance with this inventive scheme, the treatment time may be reduced without substantially changing the overall, curative biological effect of the treatment plan.